Added Explosive + TNTPrimed interface

Added Explosive (extends Entity) to Fireball
Added FusedExplosive (extends Explosive) to Creeper, MinecartTNT
Added TNTPrimed (extends FusedExplosive) (Ignite TNTBlock -> TNTPrimed)
Does it really matter whether you count from 0 to 80 or from 80 to 0?
You can still calculate ````realFuse = 80 - fuse````